This invention relates to an artificial heart valve. More specifically, this invention relates to a flexible, artificial, triple-lobed semilunar or pocketed valve intended for use in surgery to replace the natural aortic or pulmonary valve in the heart. While the valve of this invention is primarily intended for use in the human heart, it may also be of use in the hearts of animals.
For about twenty years it has been possible, in cases of heart valve inadequacy or heart valve stenosis, to replace the damaged natural heart valves by prostheses. This technique is primarily used for the replacement of all four heart-valves. Most of the prostheses developed for this purpose were ball valves or disk valves, and such valves are still predominantly being used today. These prostheses correspond to the check valves that are customarily used in technical applications. A freely movable ball or disk is disposed over an inflexible aperture which is usually circular and the ball or disk is held within a cage. When the liquid flows in the desired direction, the ball or disc lifts off from the flow aperture in the desired direction or opens through a specified angle and thus opens the outlet channel for the passage of blood. However, when the fluid flow is in the opposite direction, the ball or disk seats itself in front of the aperture and thus prevents a back flow of the blood. When used as a replacement for the natural cardiac semilunar valves, these valves have proven to operate reliably as check valves. However, a marked disadvantage is that the ball or the disk is located in the blood stream, thereby requiring lateral flow of the blood around the ball or disk thereby presenting a considerable flow resistance or drag. In comparison with the natural semilunar valve in which the flow is central, the lateral flow caused by the ball or disk leads to a substantially higher pressure drop across the valve.
For this reason, attempts have been made to develop heart valve prostheses which resemble the natural semilunar cardiac valves and, hence, offer a lower resistance to the blood flow. See, for example, D. B. Roe et al, Circulation 33, 124, (1966), Supplement I; Charles A. Hufnagel, Annals of Surgery 167, 791-95 (1968). However, these prostheses have not been fully successful in clinical practice, primarily because their closure reliability is lower than that of the customary ball valves and disk valves.
Most previously known prostheses for the replacement of heart valves have the common disadvantage of having a rigid basic structure. In the case of ball valves and disk valves, this is inherent in their construction because reliable closure requires the valve seat to have a constant shape. Even in the previously known artificial semilunar valves, the suture rings are made rigid by a metal insert so that they cannot adjust to the natural changes in size of the aorta which surrounds them after the implantation. Bellhouse, et al. disclosed in U.S. Pat. No. 3,736,598 a flexible cardiac valve having a suture ring which consists of an annular ring with three, equiangularly spaced projecting legs which extended substantially parallel to one another in the axial direction of the ring. The suture ring supports three, separate cusps. This suture ring, however, has a ring portion at the bottom thereof which interconnects the bottom portions of the projecting legs thereby preventing free, radial movement of the bottom portions with the expansion of the aortic root.
To overcome these disadvantages, the present invention seeks to develop a completely flexible artificial heart valve which has as low a flow resistance as possible but which, at the same time, operates completely reliably over long periods of time.